The present invention is related to techniques of protecting traffic on electronic and optical networks.
When a link of an electrical or optical network is broken, the traffic capacity between the two nodes of the broken link is necessarily reduced until the link is restored. Various protection techniques are used to ensure that the network connections using the link are nonetheless maintained. This is done by rerouting the signals around the broken network link, which can be performed by various protection techniques. The protection techniques rank the network connections using the link by a priority.
To the user of a network connection, the level of protection afforded to a network connection is typically defined by a Service Level Agreement (SLA) with a network Service Provider (SP), essentially the network administrator. The SLA guarantees that a network connection will have no more than a stated amount of downtime, time during which network connection is lost. The SP uses the protection priority to guarantee the desired level of protection to the user of a connection. However, the resulting service protection techniques only support one kind of guaranteed protection level: full protection with almost no downtime (termed 99.999% availability). This is true for connection-oriented technologies, such as SONET/SDH (Synchronous Optical NETwork/Synchronous Digital Hierarchy), and as well as packet flow technologies, such as MPLS (MultiProtocol Label Switching), RPR (Resilient Packet Ring), etc. Hence it should be understood that network connections as used herein includes not only circuit connections but also packet flows.
The various protection techniques theoretically allow different levels of priority so that network users with higher priority preempt users with lower priority to ensure their network connections are maintained. However, the priority levels are fixed and network connections with higher priorities simply maintain their preemption of network connections with lower priorities to ensure a “pecking order” of connectivity. The downtime of a network connection depends only on the other connections that compete with it and not on the allowed downtime of its SLA. These techniques do not necessarily ensure that the connection's downtime does not exceed its allowed downtime if the priority of the connection is not at the highest level.
Thus current protection techniques do not guarantee a network connection a level of protection below full protection. There is no way to reduce the amount of protection bandwidth and at the same time provide meaningful protection assurance for all of the connections impacted by a network failure based on each connection's SLA.